Process for preparing carboxylic acids from olefins



United States Patent 3,409,648 PROCESS FOR PREPARING CARBOXYLIC ACIDS FROM OLEFINS and Joseph Kern Mertzweiller, Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Del No Drawing. Filed July 16, 1965, Ser. No. 472,724

11 Claims. (Cl. 260-413) ABSTRACT OF THE DISCLOSURE The invention is directed to an improved process for forming chiefly 0 -0 linear organic acids by first oxonating a C C alpha or internal olefin, preferably a linear olefin, selectively to aldehydes in the presence of a More specifically, the present invention is directed to an improved process for forming C e.g., C to C organic acids composed chiefly of linear C to C organic acids by first oxonating their corresponding C alpha or linear internal olefins, e.g. C to C linear olefins, selectively to aldehydes in the presence of a suitable oxonation catalyst; and then oxidizing, e.g., with the use of air or other their corresponding C olefins or mixtures of olefins by subjecting the olefins to an oxonation-air oxidation the production of substantially linear from their corresponding C alpha olefins.

Another feature of the present invention is that we have discovered that selectivity in converting aldehydes or linear internal 3,409,648 Patented Nov. 5, 1968 A wide range of alpha olefins or linear internal olefins can be employed successfully in accordance with this invention. Thus, the following olefins can be listed as exemplary of those which can be used in accordance with this invention. Suitable responding linear C of include, but are not limited to, the following: C to C alpha or internal olefins and mixtures thereof, e.g., penetne-l, hexene-l, heptene-l, octene-l, nonene-l, decene-l, undecene-l, dodecene-l, eicosene-l, docesene-1, heptacosene-l, etc. and/or the corresponding internal iso- C to C carbon number range can characteristic composition:

ing wax within the have the following The oxonation step, wheerby the alpha or linear internal olefins or mixtures thereof are converted to their C corresponding aldehydes can be conducted readily in the presence of paraflinic solvents within the C to C range. Of course, no solvent need be employed.

This oxonation reaction can be conducted at temperatures of about 150 to about 350 F., usually is conducted at temperatures of about 150 to 250 and preferably at temperatures of about 180 toabout 220 F. in the presence of a suitable oxonation catalyst,

catalyst capable of selectively converting the olefins to their corresponding C aldehydes can be employed.

The oxonation reaction is conducted for a sufiicient period of time to substantially oxonate most of the olefins stream to aldehydes. This time can catalyst employed in conjunction with C to C alpha olefins wt. percent of the feed stream being said alpha olefins) and when the oxonation temperature is 180 to 220 F. and atmospheres, factorily in a 60 to minute reactor holding period. The lower temperatures and pressures are preferred as this favors linear aldehyde formation.

Carbon monoxide and hydrogen (synthesis gas) are fed to the oxonation reaction zone to supply the requisite tion is capable of attaining.

' been discovered that materials for the'aldehyde synthesis reaction; normally a considerable excess of both and H are used. Thus, carbon monoxide is usually supplied to allow 220 moles .of carbon monoxide per mole of olefin present in the feed stream per unit time. Preferably, the carbon monoxide feed rate is to moles of carbon monoxide per mole of olefin per unit time. Hydrogen can be fed at a feed rate of 2 to moles of hydrogen per mole of olefin per unit time. Usually, the hydrogen feed rate ranges from about 5 to 10 moles per mole per unit time. Normally the consumption ratio of H /CO is very near the theoretical 1/1 volume ratio for aldehyde synthesis; hence the mixed gases are best fed in this composition. In either batch or continuous oxonation processes, a continuous flow of the gas mixture is a convenient method of maintaining the gas composition essentially constant. The pressure in the 0x0 reaction stage is normally in the range of 50 to 30 0 atmospheres, preferably 65-200 atmospheres.

Subsequent to the oxonation step described above, the 0x0 reaction product, including the soluble cobalt octacarbonyl or other suitable oxonation catalyst, is discharged at a controlled rate from the oxonation reactor or other storage vessel into the oxidation reactor vessel, which can be a glass reactor equipped with appropriate agitation devices, such as a stirrer, and appropriate facilities for the feeding of the oxygen-containing gas thereto. The rate at which the oxygen is fed to the oxidation reaction zone is controlled by any suitable gas feeding and regulator device to insure that the proper concentration of oxygen with respect to aldehyde is maintained during the oxidation stage.

According to the present invention, at least 0.9 mole of oxygen per mole of aldehyde present in the 0x0 reac tion product per unit time must be supplied in order to obtain the selectivity of reaction which the present inven- Usually, the oxygen feed rate in a continuous flow operation ranges from about 0.90 to 32 moles of oxygen per mole of aldehyde per unit time, and preferably from 0.9 to 1.2 mole/mole/unit time. Thus, according to the present invention, it has use of oxygen supply rates below 0.9 mole/mole/unit time usually results in far inferior selectivities and acid yields. Thus, when the oxygen supply rate (oxygen feed rate) was reduced from 1.2 to 0.60 mole/mole/hr. in an oxidation stage having the same cobalt catalyst and conducted in the presence of nheptane using the same weight concentration of catalyst at the same oxidation temperatures, the 0.6 mole/mole/ hour run resulted in an acid yield of 65.5 mole percent on aldehyde present in the 0x0 reaction product feed stream to the oxidation step versus a 80.6 mole percent acid yield when the oxygen feed rate was 1.2 mole/mole/ hour.

Characteristically, the oxidation stage of the present invention can be conducted at temperatures of about 0 to about 212 F., usually at temperatures of about 32 to about 160 F., and more preferably at temperatures of about 86 to about 122 F. One to 50 atmosphere pressure can be used for oxidation, but usually the pressure maintained during the oxidation step ranges only slightly above atmospheric, e.g., 2 to 4 p.s.i. above atmospheric pressure. However, oxidations carried out at elevated pressure would increase the solubility of oxygen in the reaction solvent, hence providing even more favorable oxygen to aldehyde ratios with improvements in acid yield. Within the purview of this invention the oxidation reaction takes place essentially instantaneously so that reactor holding time is not a vital consideration.

Usually the catalyst is employed in the oxonation (1st stage) step in concentrations ranging from about 0.05 to 0.5 wt. percent cobalt catalyst (as cobalt metal based on olefins) present in the predominantly olefinic feed stream to the oxonation step. Preferably, the catalyst concentration on this basis ranges from about 0.1 10

wt. percent. Essentially none of this catalyst is lost during the transfer from the oxonation vessel to the oxidation vessel, hence essentially the same catalyst concentration is present during the oxidation step as was present during the oxonation step. As soon as the oxygen is fed to the reaction products from the oxonation step, aldehyde oxidation to the corresponding organic acid, or mixtures thereof, takes place almost immediately. Thus, e.g. the dicobalt octacarbonyl oxonation catalyst from the olefin oxonation step is used directly and converted in situ directly to the active cobalt oxidation catalyst.

An interesting and advantageous advantage of the present invention is that there appears to be a built-in refining feature which is a concomitant advantage. This built-in advantage is that the branched isomeric aldehydes present in the oxonation reaction product are at least partially converted during the oxidation step to readily separable materials when the oxidation step is conducted using the above-mentioned critical oxygen feed rates. Thus, the branched aldehydes undergo reaction to vmake high molecular weight oxygenated compounds free of carboxyl groups. These high molecular weight oxygenated compounds are high boiling, and are not soluble either in water or alkaline medium so that they are readily separable from acid products. This results in higher concentrations of linear acids in the composition of the acid product stream obtained after separation of the acids from the oxidation reaction products.

Subsequent to the oxidation step, the (linear) acid containing products stream can be decobalted to remove essentially all of the cobalt oxonation-oxidation catalyst therefrom using any suitable decobalting procedure. The recovered catalyst can then be treated to reactivate its capacity for further use.

After the decobalting of the oxidation reaction products stream has been conducted, these acid products are then extracted by treatment of the reaction products stream with a dilute sodium hydroxide-aqueous solution to separate the impurities and materials which are insoluble in water and alkali therefrom. Usually the aqueous sodium hydroxide solution contains from 5 to 25 wt. percent sodium hydroxide and more preferably from about 5 to about 10 wt. percent thereof. Then the (linear) acid product stream can be further purified by flash distillation to remove the insolubles followed by liberation of the raw product acids by addition of a suitable acid thereto, e.g. dilute hydrochloric acid. It is also within the scope of this invention to separate and purify the acids. by other suitable means, e.g. distillation, selective extraction, etc.

The present invention will be illustrated in further detail by the following examples.

Example 1 A mixture of 273.5 g. (3.25 moles) of hexene-l and 11.4 miillimoles of preformed cobalt octacarbonyl in heptane (35 g. of solution) was charged to a 1-liter stainless steel autoclave. Oxonation was then begun at a synthesis gas pressure of 1800 p.s.i.g. and at 212 F. using a synthesis gas blend containing a mole ratio of H to C0 of approximately 1.3:1. After 5 hours the uptake of synthesis gas had ceased and the reactor product, 416 g., was discharged. Analysis by gas chromatography showed a yield of aldehyde product with 81% selectivity to the linear aldehyde.

Next, a mixture of 28 g. of the 0x0 product and 300 ml. of n-heptane was charged to a glass reactor equipped with stirrer and air inlet tube (frit). Dry air was passed into the mixture at 104 F. until the characteristic green color of the active cobalt oxidation catalyst occurred (7 minutes) and until AV measurements on the exit air indicated that oxygen was no longer being consumed, i.e. the initial aldehyde charge had been used up. At this point the remainder of the aldehyde charge, 172 g., was fed to the reactor at a rate of 0.1 mole aldehyde per hour. The

air rate was regulated to supply 0.32 mole per hour. After 312 minutes the reaction was no longer exothermic, and the temperature began to drop from the 104 F. mark held previously Example 2 vent, thereby resulting in economies with respect to the solvents employed in the oxidation stage of the present invention.

Example 4 This example illustrates the built-in refining procedure aldehydes to their corresponding acids has taken place).

tabulated in Table III below.

TABLE III.-LINEAR CONTENT OF ACIDS Aldehyde Com- 4 Acid Composition position Run No. Aldehyde emp.: 104 F.; Catalyst: 0.2 Wt. Percent Cobalt; Solvent: n-Heptane] Run Aldehyde Ald. Conv. Oxygen Feed Oxygen Use Overall Acid Oxidation Rat Rat R No. Feed Rate, e, e, ate, Yield, Mole Yield, Mole Moles/Hr. Moles/Hr. Moles/Hr. Moles/Hr. Percent Percent 1 0.07 O. 32 0. 03 51.0 57. 6 2 0. l 0. 08 O. 06 0. 06 58. 0 65. 5 3 0. 1 0. 09 0. l2 0. 09 71. 5 80.6 4 0. 1 0. l0 0. 32 O. 09 73. 0 82. 4

Batch Reaction 0.1 Mole Ald.

Example 3 Thus, according to the present invention, there is an A continuous flow, oxonation-oxidation synthesis was conducted in accordance with the procedure of Example 2 above at oxygen feed rates (in air) of 0.32 mole of oxygen per mole of aldehyde per hour using an aldehyde feed rate of 0.10 mole of aldehyde per hour and a temperature of 104 F. during the oxidation (2nd stage) step. The catalyst concentration during the oxidation was 0.2 wt. percent cobalt as derived directly from the oxonation step. The four runs illustrated in this example de- TABLE II.DILUENT STUDYC0 ALDEHYDE AIR OXIDATION [Cetalystr 0.2 Wt. Percent Cobalt from the Oxonetion Step; Oz Feed Rate (in air): 0.32 mole/hr.; Aldehyde Feed Rate: 0.10 mole/hr.; Run Temp.: 104 F.]

Acid Yield, Mole Percent Diluent Composition, Wt. Percent Oxygenated Products Run N o.

Heptane As is indicated by the above data in Table II, according to a preferred embodiment of the present invention, the crude reactor product from the oxidation step can be recycled for use as a portion of the oxidation solvent to replace some or all of the paraflinic or other oxidation solinherent advantage acids obtained due in the quality (purity) of the linear the second stage (oxidation) What is claimed is: 1. A process for oxygen feed rate of at mole of said aldehydes corresponding carboxylic acids.

2. A process for preparing chiefly linear acids from a hydrocarbon feed stream comprised chiefly of C F. in the presence of a dicobalt sufiicient period of time to con- 3. A process as in claim 2 wherein said oxygen in (b) is supplied as air at an oxygen feed rate of about 0.90 to about 3.2 moles of oxygen per mole to aldehydes per unit time.

4.- A process as in claim 2 wherein the oxidation step (b). is conducted in the presence of a solvent com-prised chiefly of n-parafiins and crude oxidation reaction product from oxidation reaction (b).

5. A process as in claim 2 wherein said linear oletins are predominantly alpha olefins.

6. A process as in claim 8 wherein the oxidation step (.b) is conducted in the presence of a solvent containing oxygenated products.

7. A process as in (b) is conducted in solvent.

8. A process for preparing chiefly linear acids from C to C linear olefins which comprises (a) contacting a hydrocarbon feed stream comprised chiefly of C to C linear alpha olefins with carbon monoxide and hydrogen at a temperature of about 150 to 250 F. in the presence of a dicobalt octacarbonyl catalyst for a sufficient period of time to convert said olefins to their corresponding claim 8 wherein the oxidation step the presence of a paraffin-containing aldehydes, and (b) contacting said aldehydes with oxygen in the presence of catalyst consisting essentially of the residue of the dicobalt octacarbonyl catalyst employed in the formation of said aldehydes at temperatures of about 32 to 160 F. at pressures ranging from about 1 to atmospheres while maintaining an oxygen feed rate of about 0.90 to 3.2 moles of oxygen per mole of aldehyde per unit time. I

9. The process of claim 1 wherein the oxygen-aldehyde contacting is conducted in a continuous flow operation :and the oxygen feed rate ranges from about 0.90 to 1.2 moles of oxygen per mole of aldehyde per unit time.

10. The process of claim 2 wherein the aldehyde contacting is conduited in a continuous flow operation and the oxygen feed ranges from about 0.9 to about 1.2 moles of oxygen per mole of aldehyde per unit time.

11. The process of claim 8 wherein the oxygen aldehyde contacting is conducted in a continuous flow operation and the oxygen feed ranges from about 0.9 to about 1.2 moles of oxygen per rnole of aldehyde per unit time.

References Cited UNITED STATES PATENTS l/l964 Cull et al. 260-604 3/1958 Whitaker 260-530 

